Direct-fired tunnel furnace



June 24, 1924. 1,499,042

F. VON BICHOWSKY DIRECT FIRED TUNNEL FURNACE Filed July 31,. 1922 55116.935-8116812 lv Q INVENTOR.

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5 Sheets-Sheet 2 June 24 1924.

F. VON BICHOWSKY DIRECT FIRED TUNNEL FURNACE Filed July June 24 1924. 1,499,042

F. VON BICHOWSKY DIRECT FIRED TUNNEL FURNACE Filed July 31, 1922 5 Sheets-Sheet 3 RANAN INVENTOR. you 5/090 WJIfY A TTORNEYS.

June 24 1924.

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F. VON BICHOWSKY DIRECT FIRED TUNNEL FURNACE Filed July 51, 1922 5 Sheets-Sheet.

\ I INVENTOR. f. VONfl/CHOWS/f) ATTORNEYS.

Pawnee June 24, 1924.

UNITED STATES FOORD VON BICEO WSKY, OF GLENDALE, CALIFORNIA.

DIBECT-FIRED TUNNEL FURNACE.

Application filed July 81,

To all whom it may concern.

' Be it known'that I, FOORD VON Brorrowsxr, a citizen of the United States, and a resident of the city of Glendale, county of Los Angeles, and State of California, have invented a new and useful DirectFired Tunnel Furnace, of which the following is a specification.

My invention relates to directfired tunnel furnaces and their employment in the fixation of nitrogen in the form of nitrides, carbonitrides, c anonitrides, cyanides and the like whic are prepared by means of the action of nitrogen, nitrogen containing gases or gaseous compounds and carbon or a hydrocarbon gas or gasesor vapors upon oxy 11 containing salts.

In 1882 a nited States Letters Patent No. 269,309 was granted to Ludwig Mond for a process of preparing nitro en compounds from barium oxide by heatlng it, together with carbon and nitrogen gas, in fire clay tubes or retorts set upright in a furnace. But this process never attained commercial success due to the factthat the retorts cracked or were destroyed by the action of the flame. In order to avoid this difiiculty the Badische Anilin und Soda Fabrik disclosed in their German Patent No. 190,955 a special means of heating such retorts onsag ers, containing the above mixture, and pliicedu right in a kiln while passing nitrogen t rough them. This method has the disadvantage, however, that the process'is discontinuous in that the kiln must be heated to a high temperature andthen allowed to cool thus causing a great loss of time, even thou h special means be utilized to accomplish t ermal'economies. I v In order to render the formation of the nitrogen compounds continuous it occurred to me to employ a tunnel furnace. Such furnaces have been used for a long time in the arts as for instance in the calcining of iron ore briquettes. As is well known tunnel furnaces have a high thermal efficiency due to the fact that the entering cars are gradually heated by the roducts of comustion'as 'they approach t e firing zone and that upon leaving saidzone the wagons and contents are cooled by and impart their heat to the air to be used for combustion. The temperature in the combustion zone of such a furnace is in the vicinity of 1400 G. sufiiciently high for most chemical opera- 1922. Serial no. 518,135.

ters Patent No. 1,415,280 the employment of an indirect fired pottery tunnel oven of'the Dresslerl type for heating the reactive mass in an atmosphere of nitrogen and methane. Such an oven was not, however, in the ex erimental stage, entirely satisfactory for t is reaction for the reason that the heat exchange was indirect i. e. by radiation and convection and so the rate of gas flow had to be kept quite low due to the stronglyv endothermic reactions involved in the formation of barium cyanide or silicon nitride or titanium cyanonitride and the like; thus greatly prolonging the time'of reaction. But this was not the principal objection to such a furnace for when using small amounts of alkali metal salts in "the reaction mass as promoters or catalysts these volatilized and attacked the carborunduni fire boxes or mufliers. To make these boxes ofan alkali resisting material suchas magnesia would have been impractical as that material has but a fraction of the conductivity of carborundum and is less sturdy.

In order to'overcome these difiiculties I devised the'tunnel furnace illustrated in the accompanying. drawings, in which Figures 1 and 1 represent a longitudinal section of the furnace, Figure 2 a vertical cross-section along line 22 of Figure 1, Figure 3 a vertical cross-section along line 3-3 of Figure 1, Figure 4; a vertical crosssection along line 4-4 of Figure 1", only one-half of the section bein shown, Figure 5 a vertical cross-section a ong line 55 of Figure 1, only one-half of the section being shown, Figure 6 an enlarged view of the central portion of the arran ement shown in Figure 2, Figure 7 a side e evation of the cars used in my device and Figure 8 a cross-section through a joint used between two cars. Figure 9 15 an end viewof the lower portion .of a car with a broken section of the furnace floor showing a ate closing ofi a channel beneath the cars. igure 10 is a horizontal cross-section of the portion of my furnace shown in Figure 1, taken just below the roof of the tunnel with the cars withdrawn and showing piping and gas passages. While I have shown only the preferred form of my invention, I wish to have it understood that various changes or modifications may be made within the scope of the claims hereto attached without departing from the spirit of the invention.

The furnace (1) shown in longitudinal cross-section in Figures 1 and 1 constitutes a long tunnel through which a line of cars is moved in intermittent motions. It is provided with two sliding entrance doors (2 and 3) and two sliding outlet doors (4 and 6) the two doors allowing of the entering and the removal of a car without causing loss of heat. Throughout the furnace extend the rails (7) for the cars (8). The latter cars are ordinary four wheel trucks, one of their characteristics being that each wheel (9) rotates on an individual axle (11) so that the central portion underneath the body is left clear. Each car is further provided on the inside of the wheels with aprons (12) the lower ends of which dip into a layer (13) of sand or similar'material while the fore and rear ends of the aprons areadapted to tightly engage the fore or rear end of the next car by the tongue and groove engagement (14) illustrated in Figure 8. It Will'be understood that after the whole tunnel is filled with cars there is created a continuous channel underneath the cars and inside the rails which is practically air tightly separated from the remainder of the furnace. This channel is subdivided into three units by means of four gates (16, 17, 18 and 19), the gates 16 and 19 separating it from the outside while the gates (17 and 18) separate a central portion from the two end portions. These gates are hinged to swing on pivots (21) which may be actuated from the outside of the tunnel so that the gates may be. opened for the purpose of allowin the train of cars to move.

In iigure 10 one of the channel gates 17 is shown in closed position and another, 18, in depressed or open position. Figure 10 is a detail of one of the gates (17) looking toward the right hand end of the furnace and shows the gate closed up against the bottom of a car and fitting snugly between the apron plates 12. The means for operating the gates is indicated by the shaft 48 extending beyond the furnace walls to a handle 49.

Each car is provided with preferably six tubes (22) rather long and of small diameter, say about 6 inches, which are designed to hold the substances to be treated. The body of each car which is rather heavy and which preferably connects with the "adjoining car through a tongue and groove arrangement as shown at (23) is provided with a central port (24) connecting with branches (26) leading to the various tubes (22) so that each tube (22) is connected with the port (24) extending to the bottom of the body and registering with passages (27) in blocks (28) disposed centrally underneath the cars when the latter are in their resting positions. It will be seen that in this manner nitrogen or any other gas can be intro duced through the passage (27) and the port (24) with its branches (26) into the tubes (22) without coming in contact with the flames in the furnace.

In the general arrangement shown in Figures 1 and 1 that portion of the furnace between the gates 16 and 17 is intended for the preheating of the tubes and their contents as well as for the introduction of natural gas or whatever the particular process may call for, while the extreme heat is applied in the central portion defined between gates (Hand 18) during which time the nitrogen is introduced into the tubes. That portion enclosed between the gates 18 and 19 is utilized for heating the tubes (31) for preheating the nitrogen and further on the vertical tubes (32) for preheating the air used for the burners (33) so that when the car arrives at the end of the tunnel most of its heat units have been absorbed.

Natural gas, as has been previously stated, is introduced during the first part of the travel of the cars into the tubes by means of pipes (34) embedded preferably in the material surrounding the substructure of the cars and running parallel to the same through a suitable distance for the purpose of cooling the substructure and of preheating the gas. For the nitrogen used in the central portion of the furnace a reservoir (36) is provided underneath the furnace into which nitrogen is fed, the latter being introduced tlxough the pipe (37) from the outside of the furnace and passing through the horizontal tubes (31) into the reservoir or manifold (36). The latter is provided with preferably three outlet passages (38) communicating with the ports (24) in the car bodies.

The burner (33) may be of any suitable construction and may be made to use oil or gas. In the particular construction shown in the drawings the air used for the burner is preheated in the tubes (32) and passed through the horizontal tubes (39) and the blower (41) into the burner, the gas being introduced through a smaller pipe (42) so that the tubesof the central car are struck directly between flames. The products of combustion are carried off through the flue (44) into a stack not shown in the drawings.

By means of this construction the problem of poor heat conduction is overcome by placing the material in the tubes or retorts (22) of relatively small diameter and by subjecting them to the intense heat of the open flame. The problem of supplying the retorts with nitrogen is solved by passing the gas upwards through the body of the. car into the retorts by means of channels. .For a successful operation it is necessary that the nitrogen should be above atmospheric pressure below the cars or that the pressure around the tops of the retorts should be less than atmospheric. The latter condition would naturally prevail in a furnace sub jected to draft as in the present case. The absorption of nitrogen takes place quite rapidly even under a reduced pressure.

The substructure of the cars being such that no air can enter the channel between the wheels from the outside, it is sufficient when a loose slidingjointis employed as a connection between the source of nitrogen and the ports (24) leading to the retorts.

The operation of the device may be described as follows referring to its use in the manufacture of titanium nitrides from ilmenite. The ilmenite to be treated is made into small egg briquettes with the addition of a binder and a little sodium carbonate as a catalyst, see United States Letters Patent No. 1,408,661 granted to John Harthan and myself. These briquettes are placed in six upright retorts mounted upon each car. The retorts may be made either in one piece or 1n a number of ring segments or saggers which are stacked one on top of the other and cemented together so that in case a crack develops in one segment only that one would have to be removed. The car having been loaded the succession of steps is as follows, assuming that the furnace is filled with cars and in operation:

The newly loaded car is introduced into the receiving compartment at the left of the furnace by raising the door (2), the door (3) being down. The door (6) at the right hand of the furnace is then opened so that a car may be withdrawn, whereupon the door (6) is closed and the door (4) opened. The gates (16, 17, 18 and 19) dividing the channel, are depressed so as not to interfere with the motion of the train of cars; the door (3) .is raised and the train of cars pushed forward by the length of one car whereupon the gates in the channel are closed again and the doors (3 and 4) lowered. This operation is repeated for each additional car, or about once every six hours. As the cars thus progress in steps through the tunnel they come into posi 'on over the blocks (28) where in successive sta es they are treated with natural gas whic 1 has been warmed by passing through the pipes (34) absorbing heat units from the substructures of the cars. When they reach the nitrifying zone nitrogen containing natural gas is su plied to them from the nitrogen manifold 36) through one or more of the three passages (38), the quantity of gas being regulated by suitable sliding gates or dampers as shown at (46). This nitrogen enters to the system through the inlet (37) from the outside and then through the horizontal tube into the manifold, which latter is preferably equipped with pyrometers (47) and suitable peep holes. In the third stage, that is between the gates (18 and 19) natural gas only is supplied with-. out the addition of nitrogen. The temperature of the furnace is controlled by observation through peep holes and by radiation pyrometers or rare metal thermocouples. natural gas is not available for the reduction phase the briquettes may be made up with carbon and producer gas be used to help the reduction and also as a fuel gas if so desired.

The furnace itself is lined with magnesia brick and in the hottest zone with bricks of fused mgnesia. In this way the furnace will be unattached by alkali metal vapors in the exit gases.

It is possible of course thatthe furnace may have to be modified in slight respects to accommodate different local conditions or different substance or uses without departing from the scope of this invention. It should be understood, however, that I do not claim as my invention any of the reactive masses mentioned as they have already been covered by Letters Patent issued to others as well as myself.

I claim:

1. In a direct fired tunnel furnace, means for treating a reactive material with a gas while protecting it from the furnace flame comprising a fire resisting container enclosing the material, a car for passing the container through the furnace, and means for feeding the gas directly through the material in the container and after reactance out into the furnace.

2. In a direct fired tunnel furnace, means for treating a reactive material with a hot gas while protecting it from the furnace flame comprising a fire resistin container enclosing the material and vented to the furnace. a car for passing the container through the furnace. and means associated with the bottom of the furnace and the body of the car for feeding the gas directly through the material in the container and after reactance out into the furnace.

3. In a direct fired tunnel furnace. means for treating a reactive material with a hot gas while protecting it from the furnace flame comprising a fire resisting container enclosing the material and vented to the furnace, a car for passing the container through the furnace, means for preheating the gas, and means associated with the bottom of the furnace and the body of the car for feeding the gas directly through the material in the container and after reactance out into the furnace.

4. In a direct fired tunned furnace. means for treating a reactive material with a hot gas while protecting it from the furnace flame comprising a fire resisting tubular retort enclosing the material mounted upright on a car within the furnace, means for heating a reactive gas and means for passing same upwards through the material for reactance out of the upper end of the retort into the furnace.

In a direct fired tunnel furnace, a car having containers for a reactive material thereon, and means for directly feeding a reactive gas into said containers through the body of the car, comprisin a downwardly projecting member 0 the car adapted to be brought in juxtaposition with a corresponding member in the bottom of the furnace allowing the gas to pass there through. 6. In a direct fired tunnel furnace, a car having a retort thereon open at one end to the tunnel, means for feeding a gas directl into the retort comprising a downwar ly projecting member on the car having a port therein communicatin with the retort, means for creating a dra t through the port and retort into the tunnel, and a plurality of gas passage openings in the bottom of the furnace, said downwardly projecting member being adapted to move over and successively register with said passa es upon moving the car.

In a direct-fired tunnel furnace, a car having a retort thereon, means for feeding a as directly into the retort comprising a downwardly projecting member on the car having a port therein communicating with the retort, means for creating an upward draft through said port, a passage opening in the bottom of the furnace communicating witha source of gas, said downwardly projecting member being adapted to move over said passage registering the port therewith upon moving the car, and a chamber underneath the car enclosing within it the juncture, of the passage and ort.

p 8. In a direct fired tunnel furnace, a car having a retort thereon open at one end to the tunnel, means for feeding a gas directly into the retort comprising a downwardly projecting member on the car having a port therein communicating with the retort, means for creating a draft through the port and retort into the tunnel, a plurality of gas passage openings in the bottom of the furnace, said downwardly projecting member being adapted to move over and successively register with said passages upon moving the car, means for preheating gas and means for admitting it through th passages to the port.

9. In a direct-fired tunnel furnace, a train of cars having retorts thereon, means for feeding a gas directly into the retorts comprising a downwardly projecting membar on each car having a port therein communicating with the retorts, a plurality of openings in the bottom of the furnace communicating with a source of gas, the ports being arranged to pass over the openings for successive registering therewith, and means for preventing leakage around the junctures of the ports with the passages including the establishment of a slight suction through the ports to the furnace and a continuous channel chamber underneath the cars enclosing within it the junctures of the ports with the passages.

10. In a device of the characterdescribed, means for treating a reactive material with a gas comprising a tunnel furnace, a retort for the material, means for passing said retort through the furnace and an enclosed communicating chamber between an outside source of gas and the retort.

11. In a device of the character described, means for treating a reactive material with a gas comprising a tunnel furnace, a retort for the material, means for passing said retort through the furnace and an enclosed communicating chamber between an outside source of gas and the retort having a joint between the retort and the source of gas located therein.

12. In a device of the character described, means for treating a reactive material with a gas comprising a tunnel furnace having a track therein, a train of cars adapted to pass over said track supporting retorts for holding the material, substructures for the cars forming a continuous channel slidably engaging the bottom of the furnace and means for introducing gas from an outside source into the retorts through said channel.

13. In a device of the character described, means for treating a reactive material with a gas comprising a tunnel furnace having a track therein, a train of cars adapted to pass over said track supporting retorts for holding the material, substructures for the cars forming a continuous channel slidably engaging the bottom of the furnace, means for introducing gas from an outside source into the retorts through said channel and means for transversely subdividing the said channel.

14. In a device of the character described, means for treating a reactive material with a gas comprising a tunnel furnace having a track therein, a train of cars adapted to pass over said track supporting retorts for holding the material, substructures for the cars forming a continuous channel slidably engaging the bottom of the furnace, means for introducing gas from an outside source into the retorts through said channel and a plurality of hinged gates in the latter for transversely subdividing the same.

15. In a device of the character described, a movable car with a tubular retort of reactive material mounted thereon and open at one end, a passage through the body of the car communicating with the other end of the retort, said passage having an opening adapted to register with a stationary source of gas upon moving the car for conducting the gas through the reactive material.

16. In combination, a tunnel furnace having a plurality of ports in its bottom communicating with external sources of gas, a

10 movable car supporting a retort adapted to ass over said ports, and a passage in the ody of the car leading to the inside of the retort adapted to communicate at its lower end successively with said ports.

17. In combination, a tunnel furnace having a plurality of ports in its'bottom communicating with external sources of gas, a train of cars supporting retorts thereon adapted to pass over said bottom, and passages in the bodies of the cars leading to the inside of the retorts adapted to communicate at their lower ends with the said ports.

room) voN BIOHOWSKY. 

